The device of this invention has not been found by applicant in the prior art, and representative art which is viewed as relevant is as follows. U.S. Pat. No. 889,551 shows a forward mirror and a rear sighting device on a rifle, the sighting device not being visualized in the mirror when the rifle is incorrectly aimed. There is no provision of simultaneously finding linearly opposite reference points with this teaching. A more sophisticated device for aligning two points may be found in patents such as U.S. Pat. No. 2,307,759 and U.S. Pat. No. 2,821,104, but the structure and function is far removed from the teaching of the present invention. An illustration of representative art is U.S. Pat. No. 3,554,630 which utilizes an assembly of lenses and a mirror for establishing a reference line at right angles to the original reference line and the process known as "autocollimation". Such teaching is likewise far removed from the present invention.